This disclosure relates to air bag tethers and to a pattern-wise arrangement of such tethers in relation to air bag panels on a fabric blank, thus resulting in increased fabric utilization and an overall cost savings per finished air bag. The air bag tether system as described herein is comprised of two multi-segment congruent tether panels that are joined to one another and to a respective air bag panel. In one embodiment, the segments that comprise the tether panel that is attached to the front panel of the air bag are cut in alignment with the warp and the fill of the fabric blank. The segments that comprise the rear tether panel are cut on the bias with respect to the warp and the fill of the fabric blank. This two-panel construction, with its bias-cut segments, decreases the amount of fabric that is used in the manufacture of the air bag and tethers, while providing sufficient elongation for the tether system to be functional.
Traditionally, air bag tethers have been used to control the excursion of an air bag as it inflates. As gas is released, causing the air bag to rapidly inflate, it is necessary to keep such inflation from occurring in an uncontrolled manner. Tethers, which are sewn to the front and rear panels of an air bag, keep the inflating air bag from expanding so rapidly as to adversely affect the safety of the vehicle occupant, as the vehicle occupant contacts the air bag.
Tethers are conventionally strip-shaped pieces of fabric that are aligned in pattern-wise arrangement on a fabric blank, or that are aligned in relation to air bag panels that may be cut from the same blank. The patterns for these tethers may include a circular portion in the center area of the tether strip around which the strip is attached to the air bag panel. It is understood in the industry that such tethers should have a capacity for elongation (that is, the tethers should be able to stretch to accommodate the rapid excursion of the bag). For this reason, conventional tethers have been cut on the bias with respect to the warp and fill of the fabric. However, aligning the tether patterns to meet this criterion increases the amount of fabric needed to create an appropriate number of tethers for a plurality of air bags. Furthermore, because fabric utilization comprises more than fifty percent of the costs of a finished air bag, aligning the tethers in this manner increases production costs.
The present air bag tether system addresses the problems of fabric utilization and tether elongation. By understanding that the portions of the tether that are connected to the rear panel typically experience a greater level of stretch than the tether portions connected to the front panel, a fabric-saving solution was created. Instead of the entire tether length being cut on the bias, only those segments of the tether attached to the rear panel are cut on the bias. Using a multi-segment tether system in which only the rear tether panels are cut on the bias increases fabric utilization by allowing these bias-cut tether segments to be arranged around air bag panels into spaces which otherwise be considered fabric waste. The segments of the tether that are attached to the front panel are cut in alignment with the warp and fill of the fabric. The combination of the bias-cut and alignment-cut tether segments leads to an improved fabric utilization, while providing a tether system that is capable of sustaining the forces exerted by the inflating air bag.